Basslink has said that excess water damage into its subsea cable providing energy and wholesale high-speed telecommunications services across fibre-optic assets to Tasmania will result in repairs not being completed until mid June.

The Basslink Interconnector, the world's second-longest subsea cable, has been down since December.

The fault in the cable was discovered 90.5km from the Tasmanian coastline and removed and capped on Easter Sunday, three months after going down.

Basslink has still to determine the cause of the fault, with the company discovering that more water had leaked into the cable than expected, resulting in excess damage to the cable and requiring a third joint and more replacement cable than initially planned.

The cable repair ship will presently be returning to Geelong, Victoria, where it will stay for 10 days to pick up 100 tonnes of spare cable and specialised repair workers to take back to the fault location. New cables will be inserted where the cuts were made.

Such repairs are "highly susceptible to weather conditions", Basslink said, which is why the repair timeline has been pushed back. Prior to this, Basslink had said repairs would be done by late May.

Putting a more positive spin on the news of repair delays, Basslink chief executive Malcolm Eccles pointed out that the fault took up just 0.4 percent of the cable length.

"The analysis process, which saw us cut the cable 1,150m from the fault, has been encouraging," said Eccles.

"The team has worked hard over the last few days clearing around 63 tonnes of cable to ensure it does not interfere with the later phases of repair operations.

"We have also conducted extensive tests to confirm the removal of the fault and that the cable is ready for jointing, with both ends of the cable now capped and on the sea bed."

While ZDNet understands that TPG has since negotiated for extra bandwidth over Telstra's fibre-optic cable, the Tasmanian government got involved in the matter prior to this.

Tasmanian Minister for Information Technology and Innovation Michael Ferguson said earlier this month that the state government was "very disappointed" that TPG's group of internet service providers (ISPs) had still not made provisions for the outage, "urging them to buy more capacity on the remaining Telstra cables".

"Our understanding is that customers of TPG, which includes iiNet, Internode, and Netspace brands, have been affected, while customers of other non-Telstra ISPs are provided for," Ferguson said in a statement.

"I have spoken to TPG senior management to put forward the concerns of Tasmanian customers. I have been assured that TPG are aware of the issues and will continue to expand their use of the ample Telstra capability.

"As I stated some time ago, Telstra advised there was sufficient capacity to cater for all Tasmanian retail and wholesale customers on the two fibre bundles it owns and operates across Bass Strait."

Ferguson added that he had also "reminded" Telstra Wholesale "of the importance of constructively receiving requests for more capacity from TPG".

Telstra itself commented that it is the duty of telcos to provide continued services for their customers despite outages, with Telstra offering capacity to allow this.

"Our network between Tasmania and the mainland has capacity available for our retail and wholesale customers while Basslink's undersea cable is being repaired," a Telstra spokesperson told ZDNet.

"It is the responsibility of individual internet service providers to make appropriate arrangements for events like this so their customers continue to receive the services they expect.

"Following the Basslink cut, we have been working with impacted ISPs to provide additional capacity."

Telstra added that it cannot disclose the details of confidential commercial arrangements with its wholesaler customers.

Ferguson had also said that the Tasmanian government took its own services off the Basslink cable in early March in preparation for the cable cutting.

"Government traffic was shifted off the Basslink cable earlier this month to avoid any possibility that important government services would be interrupted when the cut was made," Ferguson said.

In addition to affecting TPG's Tasmanian telecommunications services, the Basslink outage also slowed down repairs to TPG's own submarine cable between Sydney and Guam, which experienced an outage in early February.

TPG's maintenance contract provides for relatively fast shipments based out of New Caledonia for hardware to repair any cable faults that arise; however, the maintenance ship was at the time already repairing the Basslink cable system fault.

"TPG Telecom has a maintenance agreement which provides the group access to the CS Ile De Re based in Noumea, New Caledonia. This ship is stocked with spare cables and other hardware for repairs to the cable system. We have been informed that the same ship is being used to repair the Basslink cable system," a TPG spokesperson told ZDNet last month.

"As a result of the Basslink repairs, extra delays can be expected and therefore TPG is currently considering other options for a faster repair using an alternative vessel. At this stage, TPG is not able to quote exact restoration times."

On February 17, TPG updated the issue on its website, saying it had sourced an alternative cable repair ship that had departed Taiwan for Cairns, Queensland, where it would be loaded with repair equipment.

TPG removed the outage alert for the Guam cable from its website earlier this month.

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